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Abstract:

A semiconductor light emitting device includes first and second
semiconductor layers, an active region, a transparent
electrically-conducting layer 13, a reflecting structure 20, and a first
electrode. The second semiconductor layer has a conductivity different
from the first semiconductor layer. The active region is arranged between
the first and second semiconductor layers. The transparent
electrically-conducting layer 13 is arranged on or above the first
semiconductor layer. The reflecting structure 20 is arranged on or above
the transparent electrically-conducting layer 13. The first electrode is
arranged on or above the reflecting structure 20, and electrically
connected to the first semiconductor layer. The reflecting structure 20
includes at least a reflective layer 16. An intermediate layer 17 is
interposed between the transparent electrically-conducting layer 13 and
the reflecting structure 20. The intermediate layer 17 is formed of a
material containing an element with larger ionization tendency than the
reflective layer 16.

Claims:

1. A semiconductor light emitting device comprising: a first
semiconductor layer; a second semiconductor layer that has a conductivity
different from said first semiconductor layer; an active region that is
arranged between said first and second semiconductor layers; a
transparent electrically-conducting layer that is arranged on or above
said first semiconductor layer; a reflecting structure that is arranged
on or above said transparent electrically-conducting layer; and a first
electrode that is arranged on or above said reflecting structure, and is
electrically connected to said first semiconductor layer, wherein said
reflecting structure includes at least a reflective layer, wherein an
intermediate layer is interposed between said transparent
electrically-conducting layer and said reflecting structure, wherein said
intermediate layer is formed of a material which contains an element with
larger ionization tendency than said reflective layer.

2. The semiconductor light emitting device according to claim 1, wherein
said reflective layer is formed of an electrically insulating material.

3. The semiconductor light emitting device according to claim 1, wherein
said reflective layer is formed of SiO.sub.2.

4. The semiconductor light emitting device according to claim 1, wherein
said transparent electrically-conducting layer is formed of an oxide
containing at least one element selected from the group consisting of Zn,
In, and Sn.

5. The semiconductor light emitting device according to claim 1, wherein
said transparent electrically-conducting layer is formed of ITO.

6. The semiconductor light emitting device according to claim 1, wherein
said intermediate layer has a thickness of 270 to 540 Å.

7. The semiconductor light emitting device according to claim 1, wherein
said reflecting structure includes a dielectric multilayer film that is
arranged on or above said reflective layer and is formed of a plurality
of dielectric layers, wherein said intermediate layer is formed of the
same material as a first layer of the layers which compose said
dielectric multilayer film.

8. The semiconductor light emitting device according to claim 7, wherein
said reflective layer is formed of the same material as a second layer of
the layers which compose said dielectric multilayer film.

9. The semiconductor light emitting device according to claim 1, wherein
said intermediate layer is formed of Nb2O.sub.5.

10. The semiconductor light emitting device according to claim 1 further
comprising a second electrode that is electrically connected to said
second semiconductor layer, wherein said first and second electrodes are
arranged on a first main surface side of the semiconductor light emitting
device, wherein said first main surface side serves as a mount surface
side to be mounted, and a second main surface side opposed to said first
main surface side serves as a light-outgoing surface side through which
light outgoes.

11. The semiconductor light emitting device according to claim 1 further
comprising a second electrode that is electrically connected to said
second semiconductor layer, wherein said first and second electrodes are
arranged on a first main surface side of the semiconductor light emitting
device, wherein said first main surface side serves as a light-outgoing
surface side through which light outgoes, and a second main surface side
opposed to said first main surface side serves as a mount surface side to
be mounted.

12. The semiconductor light emitting device according to claim 1, wherein
the thickness of said transparent electrically-conducting layer is
approximately an integral multiple of λ/4, where λ is the
wavelength of light emitted from said active region.

13. The semiconductor light emitting device according to claim 7, wherein
said dielectric multilayer film is formed as a multilayer structure
including two or more types of dielectric layers with different
refractive indices that are alternately formed on each other, wherein
each of the dielectric layers has thickness of 1/4 of the wavelength of
light emitted from said active region.

14. The semiconductor light emitting device according to claim 1, wherein
said reflecting structure has a superposition structure in which said
reflecting structure is sandwiched between the transparent
electrically-conducting layer and the first electrode, or a structure
that provides electrically-conductive paths and reflective areas that are
separated in the same surface.

15. The semiconductor light emitting device according to claim 1, wherein
said reflecting structure includes a dielectric multilayer film that is
arranged on or above said reflective layer and is formed of a plurality
of dielectric layers, wherein the thickness of said dielectric multilayer
film is smaller than said reflective layer.

16. A semiconductor light emitting device comprising: a first
semiconductor layer; a second semiconductor layer that has a conductivity
different from said first semiconductor layer; an active region that is
arranged between said first and second semiconductor layers; a
transparent electrically-conducting layer that is arranged on or above
said first semiconductor layer; a reflecting structure that is arranged
on or above said transparent electrically-conducting layer; and a first
electrode that is arranged on or above said reflecting structure, and is
electrically connected to said first semiconductor layer, and an
intermediate layer is interposed between said transparent
electrically-conducting layer and said reflecting structure, wherein said
intermediate layer is formed of Nb2O5, Al2O3,
TiO2, or SiN.

17. The semiconductor light emitting device according to claim 16,
wherein said reflective layer is formed of an electrically insulating
material.

18. The semiconductor light emitting device according to claim 16,
wherein said reflective layer is formed of SiO.sub.2.

19. The semiconductor light emitting device according to claim 16,
wherein said transparent electrically-conducting layer is formed of an
oxide containing at least one element selected from the group consisting
of Zn, In, and Sn.

20. The semiconductor light emitting device according to claim 16,
wherein said transparent electrically-conducting layer is formed of ITO.

21. The semiconductor light emitting device according to claim 16,
wherein said intermediate layer has a thickness of 270 to 540 Å.

22. The semiconductor light emitting device according to claim 16,
wherein said reflecting structure includes a dielectric multilayer film
that is arranged on or above said reflective layer and is formed of a
plurality of dielectric layers, wherein said intermediate layer is formed
of the same material as a first layer of the layers which compose said
dielectric multilayer film.

23. The semiconductor light emitting device according to claim 22,
wherein said reflective layer is formed of the same material as a second
layer of the layers which compose said dielectric multilayer film.

24. The semiconductor light emitting device according to claim 16,
wherein said intermediate layer is formed of Nb2O.sub.5.

25. The semiconductor light emitting device according to claim 16 further
comprising a second electrode that is electrically connected to said
second semiconductor layer, wherein said first and second electrodes are
arranged on a first main surface side of the semiconductor light emitting
device, wherein said first main surface side serves as a mount surface
side to be mounted, and a second main surface side opposed to said first
main surface side serves as a light-outgoing surface side through which
light outgoes.

26. The semiconductor light emitting device according to claim 16 further
comprising a second electrode that is electrically connected to said
second semiconductor layer, wherein said first and second electrodes are
arranged on a first main surface side of the semiconductor light emitting
device, wherein said first main surface side serves as a light-outgoing
surface side through which light outgoes, and a second main surface side
opposed to said first main surface side serves as a mount surface side to
be mounted.

27. The semiconductor light emitting device according to claim 16,
wherein the thickness of said transparent electrically-conducting layer
is approximately an integral multiple of λ/4, where λ is the
wavelength of light emitted from said active region.

28. The semiconductor light emitting device according to claim 22,
wherein said dielectric multilayer film is formed as a multilayer
structure including two or more types of dielectric layers with different
refractive indices that are alternately formed on each other, wherein
each of the dielectric layers has thickness of 1/4 of the wavelength of
light emitted from said active region.

29. The semiconductor light emitting device according to claim 16,
wherein said reflecting structure has a superposition structure in which
said reflecting structure is sandwiched between the transparent
electrically-conducting layer and the first electrode, or a structure
that provides electrically-conductive paths and reflective areas that are
separated in the same surface.

30. The semiconductor light emitting device according to claim 16,
wherein said reflecting structure includes a dielectric multilayer film
that is arranged on or above said reflective layer and is formed of a
plurality of dielectric layers, wherein the thickness of said dielectric
multilayer film is smaller than said reflective layer.

Description:

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

[0001] This application claims priority to Japan Application Nos.
2011-086821 and 2012-025525, filed Apr. 8, 2011 and Feb. 8, 2012, the
contents of which are incorporated herein by reference in their entirety.

[0005] Semiconductor light emitting devices can be small and highly
effective in power consumption, and can emit vivid color light. In
addition, in the case of light emitting devices of semiconductor devices,
there are no concerns about bulb burnout and the like. In addition,
semiconductor light emitting devices have features such as excellent
initial driven characteristics, resistance to vibration or ON/OFF
repeats. Since semiconductor light emitting devices have these excellent
features, semiconductor light emitting devices such as light emitting
diode (hereinafter, occasionally referred to as "LED") and laser diode
(hereinafter, occasionally referred to as "LD") have been used as various
types of light sources. In particular, in recent years, light emitting
diodes receive attention as light source for lighting replacement of
fluorescent lamps, in other words, as next-generation lighting having
long life and low power consumption. From this viewpoint, further
improvement is required in light output and light emission efficiency.

[0006] In order to improve outgoing efficiency of light emission, the
inventors have been developed a flip-chip type light emitting device
which has a reflective film with improved reflectivity, the flip-chip
type light emitting device having electrode surfaces opposed to a mount
surface (Laid-Open Patent Publication No. JP 2009-164,423). As shown in a
cross-sectional view of FIG. 8A and an enlarged view of FIG. 8B, the
light emitting device disclosed in this document includes a semiconductor
structure 11 which has light-emitting layer 8, a light-outgoing surface
18 which is arranged on one of the main surfaces of the semiconductor
structure 11, and electrodes 3 which are arranged on the other main
surface opposed to the light-outgoing surface 18 and are electrically
connected to the semiconductor structure 11. In the light emitting
device, a reflecting structure 20 is formed between the semiconductor
structure 11 and each of the electrodes 3. The reflecting structure 20
includes a reflective layer 16 which is formed above the semiconductor
structure 11, and a dielectric multilayer film 4 which is arranged on
this reflective layer 16 and is composed of a plurality of dielectric
layers. The refractive index of the reflective layer 16 is smaller than
the refractive index of the semiconductor structure 11. The center
wavelength of the reflection spectrum of the reflecting structure 20 is
longer than the light emission peak wavelength of the light-emitting
layer 8. According this construction, it is possible to provide a
reflecting structure which can be thin but can have excellent
weatherability and high reflectivity.

[0008] As stated above, in the case of semiconductor light emitting
devices, since there are no concerns about bulb burnout and the like as
compared with light bulbs, in addition to this feature, further
improvement is required in durability or reliability so that the
semiconductor light emitting devices can be virtually maintenance-free.
However, semiconductor light emitting devices have a disadvantage that
the forward voltage in the operation will gradually rise as the use time
of the semiconductor light emitting devices. If the forward voltage
rises, the loss will be large so that the heat amount will be large. Heat
dissipation is important for semiconductor light emitting devices. If the
heat amount of semiconductor light emitting devices becomes large, this
will affect the life of the products. Generally, if the forward voltage
rises 10% or more, it is judged that failure occurs. In particular, in
recent years, it is required to reduce power consumption. Also, from this
viewpoint, increase of driving voltage is undesirable.

[0009] The present invention is aimed at solving the problem. It is a main
object of the present invention to provide a semiconductor light emitting
device which is excellent in life characteristic, and can suppress rise
of forward voltage.

SUMMARY OF THE INVENTION

[0010] To achieve the above object, a semiconductor light emitting device
of a first aspect of the present invention includes a first semiconductor
layer, a second semiconductor layer, an active region, a transparent
electrically-conducting layer 13, a reflecting structure 20, and a first
electrode. The second semiconductor layer has a conductivity different
from the first semiconductor layer. The active region is arranged between
the first and second semiconductor layers. The transparent
electrically-conducting layer 13 is arranged on or above the first
semiconductor layer. The reflecting structure 20 is arranged on or above
the transparent electrically-conducting layer 13. The first electrode is
arranged on or above the reflecting structure 20, and is electrically
connected to the first semiconductor layer. The reflecting structure 20
includes at least a reflective layer 16. An intermediate layer 17 is
interposed between the transparent electrically-conducting layer 13 and
the reflecting structure 20. The intermediate layer 17 is formed of a
material which contains an element with larger ionization tendency than
the reflective layer 16. According to this construction, since the
intermediate layer is interposed between the transparent
electrically-conducting layer and the reflecting structure, it can be
suppressed that the forward voltage in the operation gradually rises with
the use time of the semiconductor light emitting devices. Therefore, it
is possible to provide advantages that reliability and durability are
improved. In particular, the transparent electrically-conducting layer
can be resistant to oxidation. As a result, it is possible to suppress
increase of the resistance, i.e., rise of Vf.

[0011] In a semiconductor light emitting device of a second aspect of the
present invention, the reflecting structure 20 can include a dielectric
multilayer film 4 that is arranged on or above the reflective layer 16
and is formed of a plurality of dielectric layers, and the thickness of
the dielectric multilayer film can be smaller than the reflective layer.

[0012] In a semiconductor light emitting device of a third aspect of the
present invention, the reflective layer 16 can be formed of SiO2.

[0013] In a semiconductor light emitting device of a fourth aspect of the
present invention, the transparent electrically-conducting layer 13 can
be formed of ITO.

[0014] In a semiconductor light emitting device of a fifth aspect of the
present invention, the intermediate layer 17 can be formed of
Nb2O5, Al2O3, or TiO2. According to this
construction, since the transparent electrically-conducting layer 13 is
covered by the material which contains an element with larger ionization
tendency than the reflective layer, the transparent
electrically-conducting layer can be resistant to oxidation. As a result,
it is possible to suppress increase of the resistance, i.e., rise of Vf.
Therefore, it is possible to improve the life and the reliability of the
device.

[0015] In a semiconductor light emitting device of a sixth aspect of the
present invention, the intermediate layer 17 can have a thickness of 270
to 540 A. According to this construction, the initial characteristic and
the life characteristic can be ensured in a good balance. Also, the sheet
resistance of the transparent electrically-conducting layer can be
smaller.

[0016] In a semiconductor light emitting device of a seventh aspect of the
present invention, the intermediate layer can be formed of the same
material as any of the layers which compose the dielectric multilayer
film. According to this construction, since the intermediate layer is
formed of the same material as any of the layers, which are deposited on
or above the intermediate layer, any additional target material is not
required when the intermediate layer is deposited in the manufacturing
process. Therefore, it is possible to provide an advantage that the
manufacturing cost is lower.

[0017] In a semiconductor light emitting device of an eighth aspect of the
present invention, the intermediate layer 17 can be formed of
Nb2O5.

[0018] In a semiconductor light emitting device of a ninth aspect of the
present invention, a second electrode can be provided which is
electrically connected to the second semiconductor layer. The first and
second electrodes can be arranged on a first main surface side of the
semiconductor light emitting device. The first main surface can serve as
a mount surface to be mounted, while a second main surface opposed to the
first main surface can serve as a light-outgoing surface through which
light outgoes. According to this construction, in a flip-chip type
semiconductor light emitting device, it is possible to suppress rise of
forward voltage.

[0019] In a semiconductor light emitting device of a tenth aspect of the
present invention, a second electrode can be provided which is
electrically connected to the second semiconductor layer. The first and
second electrodes can be arranged on a first main surface side of the
semiconductor light emitting device. The first main surface can serve as
a light-outgoing surface through which light outgoes, while a second main
surface opposed to the first main surface can serve as a mount surface to
be mounted. According to this construction, in a face-up type
semiconductor light emitting device, it is possible to suppress rise of
forward voltage.

[0020] Also, a semiconductor light emitting device of an eleventh aspect
of the present invention includes a first semiconductor layer, a second
semiconductor layer, an active region, a transparent
electrically-conducting layer 13, a reflecting structure 20, and a first
electrode. The second semiconductor layer has a conductivity different
from the first semiconductor layer. The active region is arranged between
the first and second semiconductor layers. The transparent
electrically-conducting layer 13 is arranged on or above the first
semiconductor layer. The reflecting structure 20 is arranged on or above
the transparent electrically-conducting layer 13. The first electrode is
arranged on or above the reflecting structure 20, and is electrically
connected to the first semiconductor layer. An intermediate layer 17 is
interposed between the transparent electrically-conducting layer 13 and
the reflecting structure 20. The intermediate layer 17 is formed of
Nb2O5, Al2O3, TiO2, or SiN.

[0021] The above and further objects of the present invention as well as
the features thereof will become more apparent from the following
detailed description to be made in conjunction with the accompanying
drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] FIG. 1 is a cross-sectional view schematically showing a light
emitting apparatus according to a first embodiment;

[0023] FIG. 2A is a cross-sectional view showing a light emitting device
according to the first embodiment;

[0027] FIG. 5 is a graph showing relationship between the thickness of a
reflective layer and the relative luminous flux value;

[0028] FIG. 6 is a cross-sectional view showing the structure of a sample
used in a shearing experiment;

[0029] FIG. 7 is a graph showing the results of the shearing experiment
according to an example 1 and a comparative example 1;

[0030] FIG. 8A is a cross-sectional view showing a known semiconductor
light emitting device; and

[0031]FIG. 8B is a partial enlarged view of the light emitting device
shown in FIG. 8A.

DETAILED DESCRIPTION OF THE EMBODIMENT(S)

[0032] The following description will describe embodiments according to
the present invention with reference to the drawings. It should be
appreciated, however, that the embodiments described below are
illustrations of a semiconductor light emitting device used therein to
give a concrete form to technical ideas of the invention, and a
semiconductor light emitting device of the invention is not specifically
limited to description below. In this specification, reference numerals
corresponding to components illustrated in the embodiments are added in
"Claims" and "Summary" to aid understanding of claims. However, it should
be appreciated that the members shown in claims attached hereto are not
specifically limited to members in the embodiments. Unless otherwise
specified, any dimensions, materials, shapes and relative arrangements of
the parts described in the embodiments are given as an example and not as
a limitation. Additionally, the sizes and the positional relationships of
the members in each of drawings are occasionally shown larger
exaggeratingly for ease of explanation. Members same as or similar to
those of this invention are attached with the same designation and the
same reference numerals, and their description is omitted. In addition, a
plurality of structural elements of the present invention may be
configured as a single part that serves the purpose of a plurality of
elements, on the other hand, a single structural element may be
configured as a plurality of parts that serve the purpose of a single
element.

[0033] Also, the term "on [or above]" (e.g., on or above a layer) used in
the specification is not limited to the state where a member is formed in
contact with a layer but occasionally includes the state where a member
is formed upward relative to a layer to be spaced away from the layer, in
other words, the state where a member is formed to interpose an
interposed member between the member and the layer in an inclusive sense.
Also, the description of some of examples or embodiments may be applied
to other examples, embodiments or the like.

First Embodiment

[0034] FIG. 1 is a cross-sectional view showing a light emitting apparatus
1 according to a first embodiment of the present invention. This
illustrated light emitting apparatus 1 includes a light emitting device
10 of an LED chip, which is a sort of nitride semiconductor device. This
LED chip is mounted onto a wiring board 9, which is a sort of submount,
in a flip chip mounting manner. The flip chip mounting manner refers to a
mounting manner where a growth substrate 5 serves as a light outgoing
surface through which light outgoes. Semiconductor layers are deposited
on the growth substrate side. The growth substrate is opposed to an
electrode formation surface on which an electrode is formed. The flip
chip mounting manner is also referred to as facedown mounting manner. The
light emitting device 10 is shown upside down in FIG. 1 for illustrating
the flip chip mounting manner.

[0035] FIG. 2 is a cross-sectional view schematically showing the light
emitting device 10 shown in FIG. 1 before the light emitting device is
mounted to the light emitting apparatus, in other words, with the growth
substrate 5 facing downward and a semiconductor structure 11 being
arranged upward relative to the growth substrate. In the manufacturing
process of this light emitting apparatus, in practice, the nitride
semiconductor device is mounted with the layers on the upper surface of
the growth substrate 5 being orientated upside down as shown in FIG. 1.
The following description will schematically describe the light emitting
device 10 with reference to FIG. 2. Members that are configured similarly
to the members of the light emitting device 10 shown in FIG. 1 are
attached with the same reference numerals as the corresponding members of
the light emitting device 10 shown in FIG. 2, and their description is
omitted for sake of brevity.

[0036] The light emitting device 10 includes the semiconductor structure
11 including a light-emitting layer 8. In the light emitting device 10
shown in FIG. 2, nitride semiconductor layers are deposited on or above
one of a pair of main surfaces of the growth substrate 5, which are
opposed to each other. The nitride semiconductor layers compose the
semiconductor structure 11. Specifically, the semiconductor structure 11
of the light emitting device 10 includes a first nitride semiconductor
layer 6, the active layer 8, and a second nitride semiconductor layer 7,
which are laminated on the upper surface side of the growth substrate 5,
in this order. In addition, first and second electrodes 3A and 3B are
formed and electrically connected to the first and second nitride
semiconductor layers 6 and 7, respectively. When electric power is
supplied to the light emitting device 10 from an external source through
the first and second electrodes 3A and 3B, the active layer 8 emits light
so that the light outgoes mainly through the bottom surface side of the
growth substrate 5 as viewed in FIG. 2A. That is, in the case of the
light emitting device 10 shown in FIG. 2A, the other (bottom side in FIG.
2A) of the main surfaces of the growth substrate 5 serves as a main
light-outgoing surface 18 through which the light mainly outgoes. The
other of main surfaces is opposed to a mount surface (top side in FIG.
2A) where the electrodes 3A and 3B are formed.

[0037] Each of a pair of electrodes 3, which are of the first and second
electrodes 3A and 3B, includes a reflecting structure 20. For example,
the reflecting structure 20 can include a dielectric multilayer film 4
having a multilayer structure. FIG. 2B is an enlarged sectional view
showing a part around the dielectric multilayer film 4, which is shown by
the circle in FIG. 2A. As shown in FIG. 2B, the dielectric multilayer
film 4 has the multilayer structure including a plurality of dielectric
layers 4a. Each of the dielectric layers 4a is composed of a set of two
or more material layers 4n and 4m the refractive indices of which are
different from each other. Thus, a plurality of sets of material layers
4n and 4m are laminated on one after another. The dielectric multilayer
film 4 is arranged at least partially in the area between the
semiconductor structure 11 and each of the electrodes 3. The dielectric
multilayer film 4 is divided into parts, which are spaced away from each
other in the horizontal direction. The dielectric multilayer film 4 can
selectively reflect light with a desired wavelength. The specific
structure of the dielectric multilayer film 4 will be described later.
The center wavelength λ of the reflection spectrum of the
dielectric multilayer film (DBR) 4 according to the first embodiment is
longer than the peak wavelength λp of the light emitted from
the light-emitting layer 8.

(Light Emitting Device)

[0038] For example, in the case where the light emitting device 10 is a
nitride semiconductor device as LED shown in FIG. 2, the light emitting
device includes a sapphire substrate as the growth substrate 5, the
nitride semiconductor structure 11, and a transparent
electrically-conducting layer 13 which is formed on or above the
semiconductor structure 11. The semiconductor structure 11 includes an
n-type semiconductor layer as the first nitride semiconductor layer 6,
and a light-emitting layer as the active layer 8, and a p-type
semiconductor layer as the second nitride semiconductor layer 7, which
are epitaxially grown on or above the sapphire substrate in this order.

[0039] Subsequently, the light-emitting layer 8 and the p-type
semiconductor layer 7 are selectively partially removed by etching so
that the n-type semiconductor layer 6 is partially exposed. An n-type pad
electrode as the first electrode 3A is formed on the partially exposed
part of the n-type semiconductor layer. A p-type pad electrode as the
second electrode 3B is formed on the same surface side as the n-type
electrode 3A on or above the transparent electrically-conducting layer
13. In addition, only predetermined areas of the n-type and p-type pad
electrode 3A and 3B are selectively exposed so that the other areas of
the n-type and p-type pad electrode 3A and 3B are covered by an
electrically-insulating protective film. The n-type pad electrode may be
formed in the partially exposed part of the n-type semiconductor layer 6
with the transparent electrically-conducting layer 13 being interposed
between the n-type pad electrode and the n-type semiconductor layer. The
following description will specifically describe components of the
semiconductor light emitting device 1.

(Growth Substrate)

[0040] The growth substrate 5 is a substrate on which the semiconductor
structure 11 can be grown. The size, thickness, and the like of the
growth substrate are not specifically limited. The substrate for nitride
semiconductor can be electrically-insulating substrates (e.g., sapphire
having C-facet, R-facet or A-facet as primary surface and spinel
(MgAl2O4)), silicon carbide (6H, 4H, 3C), silicon, ZnS, ZnO,
Si, GaAs, diamond, oxide substrates (for example, lithium niobate and
neodymium gallate, which are bondable with nitride semiconductor in a
lattice-matching manner), and nitride semiconductor substrates (e.g., GaN
and AlN). Also, the substrate for nitride semiconductor may be off-angled
nitride semiconductor substrates (for example, off-angled 0.01° to
3.0° relative to the C-facet of sapphire). In addition, the growth
substrate 5 can be removed to form a substrate-less semiconductor
structure after the light emitting device construction is formed on the
growth substrate. Also, the thus-formed substrate-less semiconductor
structure can be bonded onto a support substrate (e.g.,
electrically-conductive substrate) or bonded onto a support substrate in
a flip-chip manner. Also, the thus-formed substrate-less semiconductor
structure can be bonded onto other transparent members/transparent
substrates. Specifically, in the case where the growth substrate and the
bonded member/substrate are arranged on the light-outgoing main surface
side of the semiconductor structure, they are required to be transparent.
In this case, if the growth substrate is not transparent, or cuts off or
absorbs light, it is necessarily removed. If the semiconductor structure
is bonded onto the bonded component/substrate which is not transparent,
or cuts off or absorbs light, the bonded component/substrate is
necessarily arranged on the light reflection main surface side of the
semiconductor structure. In the case where electric power is supplied to
the semiconductor structure through the transparent substrate/member on
the light outgoing side, the transparent substrate/member is required to
be electrically conductive. In addition to this, the semiconductor
structure may be bonded onto and covered by a transparent member such as
glass and resin so that the semiconductor structure is supported by the
transparent member. For example, the growth substrate can be removed by
grinding or LLO (Laser Lift Off) with the semiconductor light emitting
device being retained by a retaining device or on the chip mount part of
the submount. Even in the case the growth substrate is transparent but
different type from the semiconductor structure, it is preferable that
the substrate is removed. The reason is the substrate removal can improve
the light outgoing efficiency and the output of the light emitting
device.

(Semiconductor Structure)

[0041] The semiconductor structure 11 is preferably formed of a nitride
semiconductor in the case where the light emitting apparatus includes the
nitride semiconductor layers and a light conversion member (phosphor
etc.) used together. The nitride semiconductor can emit short-wavelength
visible light, near-ultraviolet light, or light with wavelength shorter
than them. The nitride semiconductor will be discussed later in an
example. The semiconductor structure is not limited to this. The
semiconductor structure may be formed of other semiconductors such as
InGaAs group semiconductor and GaP group semiconductor.

(Light Emitting Device Construction)

[0042] The light emitting device construction of the semiconductor layers
preferably has the active layer between the first electrically-conductive
type (n-type) layer and the second electrically-conductive type (p-type)
layer discussed later from viewpoint of output and efficiency. However,
the light emitting device construction is not limited to this, and can be
the construction discussed later or other types of light emitting device
construction. Each electrically-conductive type layer may partially
include an electrically-insulating structure, a
semi-electrically-insulating structure or an opposite
electrically-conductive type structure. Also, the first
electrically-conductive type layer and the second electrically-conductive
type layer may be additionally provided with an electrically-insulating
structure, a semi-electrically-insulating structure or an opposite
electrically-conductive type structure. Also, the first
electrically-conductive type layer and the second electrically-conductive
type layer may be additionally provided with other circuit structure such
as protection structure. The aforementioned substrate may serve as a part
of an electrically-conductive type layer.

[0043] The electrodes for the first electrically-conductive type (n-type)
layer and the second electrically-conductive type (p-type) layer are
preferably arranged on one of the main surface sides as discussed later
in the example. However, the electrodes are not limited to this
arrangement. The electrodes may be arranged on the both main surface
sides of the semiconductor structure, and be opposed to each other. For
example, one of the electrodes may be arranged on the removal side of the
aforementioned substrate-removed structure.

[0044] The semiconductor layer construction can include homo junction
structure, hetero junction structure, or double-hetero junction structure
having MIS junction, PIN junction or PN junction. The layer can have a
super-lattice structure. Also, the active layer as light emitting layer 8
can have a quantum well structure including a thin layers for quantum
effect.

(Nitride Semiconductor Layers)

[0045] The nitride semiconductors are formed of general formula
InxAlyGa.sub.1-x-yN (0≦x, 0≦y, x+y≦1), and
can be mixed with B, P, or As. The n-type semiconductor layer 6 and the
p-type semiconductor layer 7 are not specifically limited to a single
layer or multilayer structure. In the semiconductor structure 11, the
active layer as light emitting layer 8 is included. This active layer has
a single quantum well (SQW) or multi-quantum well structure (MQW). The
semiconductor structure 11 is now described in detail.

[0046] The n-type nitride semiconductor layer and the p-type nitride
semiconductor layer are formed on or above the growth substrate with the
active layer being interposed between the p-type and n-type layers. A
primary layer such as buffer layer of nitride semiconductor is interposed
between the growth substrate and the nitride semiconductor layer. The
primary layer can be formed of a low-temperature growth thin layer GaN
and a GaN layer, for example. For example, the n-type nitride
semiconductor layer can be formed of an n-type contact layer of Si-doped
GaN, and an n-type multilayer film of GaN/InGaN. The p-type nitride
semiconductor layer can be formed of an Mg-doped p-type multilayer film
of InGaN/AlGaN and a p-type contact layer of Mg-doped GaN.

[0047] For example, the light-emitting layer (active layer) 8 of the
nitride semiconductor has a quantum well structure which includes well
layers of AlaInbGa.sub.1-a-bN (0≦a≦1,
0≦b≦1, a+b≦1) and barrier layers of
AlcIndGa.sub.1-c-dN (0≦c≦1, 0≦d≦1,
c+d≦1). The nitride semiconductor used for the active layer can be
non-doped, n-type-impurity doped, or p-type-impurity doped. It is
preferable that non-doped or n-type-impurity doped nitride semiconductor
is used for the active layer. The reason is that non-doped or
n-type-impurity doped nitride semiconductor can increase the output of
the light emitting device. The barrier layer is formed of a nitride
semiconductor having a larger band gap energy than the well layer. In the
case where the well layer contains Al, it is possible to emit light with
wavelength shorter than 365 nm corresponding to the band gap energy of
GaN. The wavelength of the light emitted from the active layer can be
designed about 360 to 650 nm depending on the application of the light
emitting device, preferably 380 to 560 nm.

[0048] The well layer can be suitably formed of composition InGaN, which
is suitable for visible or near-ultraviolet light emission. In this case,
the barrier layer can be suitably formed of composition GaN or InGaN. The
well layer preferably has a thickness not less than 1 nm and not more
than 30 nm, more preferably not less than 2 nm and not more than 20 nm.

[0049] A mask with a predetermined shape is formed on the surface of the
p-type semiconductor layer 7. The p-type semiconductor layer 7 and the
active layer as light-emitting layer 8 are partially removed by etching.
Thus, a predetermined part of the n-type contact layer is exposed which
composes the n-type semiconductor layer 6.

(Light Reflection Structure)

[0050] The basic structure of the light emitting device according to the
present invention is now described. Specifically, one of the two main
surfaces of the semiconductor structure opposed to each other is the
light outgoing side, and another is the light reflection side. The light
reflection structure is arranged on the light reflection side, in
particular, in an area where a light emitting structure such as the
active layer is arranged.

[0051] The light reflection structure is formed as a part of electrode
structure, a superposition structure in which the light reflection
structure is sandwiched between electrode structures (e.g., the
transparent electrically-conducting layer 13 and a later-discussed metal
electrode layer 23), a coplanar separation structure in which the light
reflection structure is separated from an electrode structure in the same
surface, or a combination structure which combines them with each other.
Preferably, the light reflection structure is formed as the superposition
structure so as to increase the light emitting area corresponding to the
light emitting structure, and improve electric charge injection
efficiency. Specifically, the reflecting structure 20 is arranged between
the transparent electrically-conducting layer 13 and the metal electrode
layer 23 as the external connection (pad) electrode. The transparent
electrically-conducting layer 13 is formed as the electrode arranged on
the semiconductor layer contact side. The external connection (pad)
electrode will be connected to a source arranged external of the device.
The reflecting structure 20 between the electrodes (the transparent
electrically-conducting layer (transparent electrode) and pad electrode)
has a shape which allows the electrodes to be electrically conductive to
each other (for example, a shape having openings). Specifically, it is
preferable that electrically-conductive paths and reflective areas are
separated in the same surface as discussed later. However, the reflecting
structure is not limited to this. The reflecting structure may be formed
as an electrically-conductive reflective structure. In the coplanar
separation structure, electrically-conductive structures are formed in
separation areas, the reflecting structure 20 can be formed of
electrically-insulating materials. On the other hand, if the electrode is
arranged on the light outgoing side, the electrode can be partial
electrodes, a light-transmissible electrode, a transparent electrode, or
a structure which combines them with each other.

[0052] The reflecting structure 20 in the present invention includes a
reflective portion having reflectivity which varies depending on the
wavelength of emitted light. Specifically, the reflecting structure
includes a later-discussed dielectric multilayer film, DBR, or the like.
In addition to the wavelength-dependent reflective portion, the
reflecting structure can additionally include a transparent film and a
metal reflective layer. The transparent film has a refractive-index
difference from the semiconductor layer and the transparent member (the
wavelength-dependent reflective portion or the electrode) so that light
can be reflected by the refractive-index difference. In this case, the
transparent film is arranged on the semiconductor layer side, while the
light-impervious metal reflective layer is arranged outside the
transparent film. The arrangement of the wavelength-dependent film and
the transparent film is not specifically limited. However, in the case
where the transparent film and the wavelength-dependent film are arranged
from the semiconductor layer side in this order, it is possible to
separately provide the reflection function of the transparent film by the
refractive-index difference, and the wavelength-dependent and
direction-dependent reflection function of the wavelength-dependent film.
This case is preferable since both the functions can be improved.

[0053] In the light emitting device 10 shown in FIG. 2, the reflecting
structures 20 formed under both the electrodes 3 (more preferably the
optical characteristic of the reflecting structures 20) are substantially
same. According to this construction, since the reflecting structures 20
under both the electrodes are substantially same, the color unevenness of
the light emitting apparatus 1 as light source can be reduced. In
addition to this, the manufacturing process can be simplified.
Alternatively, the reflecting structures 20 formed under the electrodes
3A and 3B may have optical characteristic difference. For example, the
thickness of the transparent film can be determined in consideration of
the light incidence angle depending on location of electrode, the
distance between the transparent film and the wavelength conversion
member, which can be included in a covering layer, and the like.

[0054] It should be noted that the reflecting structure is not limited to
a structure which includes only one film/member for each film/member
type. The reflecting structure can be formed as a multiplex structure,
for example, a superposition structure which includes a plurality of
reflecting structures having respective types of films/members repeatedly
arranged on one after another, or a structure which includes a plurality
sets of respective types of films/members or multiplexed respective types
of films/members. The following description will describe a reflecting
structure which includes respective types of films/members formed
integrally with each other. However, the reflecting structure is not
limited to this. The respective types of films/members may have different
shapes/patterns from each other. In a superposition reflecting structure,
for example, a first reflecting structure group having dot-shaped
openings as shown in FIG. 3 is arranged under a second reflecting
structure group with the transparent electrically-conducting layers 13
such as ITO being interposed between the first and second reflecting
structure groups. In this case, it is preferable that the second
reflecting structure group at least partially overlaps the opening areas
of the first reflecting structure group as viewed in cross-section.
According to this construction, the formation area of reflecting
structures increases as viewed in plan view from the electrode side. As a
result, the reflective efficiency can be improved, and the light outgoing
efficiency can be increased.

[0055] Although the reflecting structure has been described which is
arranged corresponding to the light emitting structure, the reflecting
structure is not limited to this. The reflecting structure can be
arranged in a non-light emission area such as n-electrode area, the side
surfaces of the semiconductor layers or the side surfaces of the light
emitting structure, or device surfaces. For example, the reflecting
structure can be arranged overlapping the protective film. The following
description will describe the transparent electrically-conducting layer
13, the reflecting structure 20, the electrode 3, and the protective
film.

(Transparent Electrically-Conducting Layer 13)

[0056] The transparent electrically-conducting layer 13 is mainly formed
on or above the p-type semiconductor layer 7. For example, in the case
where the electrically-conducting layer is formed almost all over the
p-type semiconductor layer 7 and the exposed n-type semiconductor layer
6, a current can uniformly spread all over the p-type semiconductor layer
7. In addition, since the electrically-conducting layer is transparent,
the reflecting structure can be additionally arranged on the
electrically-conducting layer. The covering area of the transparent
electrically-conducting layer 13 may be one of the n-type semiconductor
layer 6 and the p-type semiconductor layer 7.

[0057] Although many sorts of transparent electrodes are known, the
transparent electrically-conducting layer 13 preferably is formed of an
oxide containing at least one element selected from the group consisting
of Zn, In and Sn. Specifically, it is preferable that the transparent
electrically-conducting layer 13 is formed of an oxide containing Zn, In
or Sn such as ITO, ZnO, In2O3, SnO2. In particular, the
transparent electrically-conducting layer 13 is more preferably formed of
ITO. In this case, the transparent electrically-conducting layer can be
in good ohmic contact with the member to be contacted. Alternatively, the
transparent electrically-conducting layer may be a metal thin film of Ni
or the like with thickness 3 nm. Also, the transparent
electrically-conducting layer may be a thin film of oxide or nitride of
other metal, or compound of them. Also, the transparent
electrically-conducting layer may be a light-transmissible structure such
as a metal film having openings as windows. Also, the transparent
electrically-conducting layer may be a combination structure which
combines these features with each other. Thus, the
electrically-conducting layer is formed almost all over the
electrically-conductive semiconductor layer, for example, the p-type
semiconductor layer, so that a current can uniformly spread all over the
layer.

[0058] The thickness of the transparent electrically-conducting layer 13
can be determined in consideration of the light absorption and
electrical/sheet resistance of the semiconductor layer, in other words,
the light reflective structure and current spread of the semiconductor
layer. For example, the thickness of the transparent
electrically-conducting layer 13 can be not more than 1 μm,
specifically, 10 to 500 nm. In addition, it is preferable that the
thickness of the transparent electrically-conducting layer is an integral
multiple of λ/4 (λ is the wavelength of light emitted from
the active layer 8). In this case, the light outgoing efficiency can be
increased.

(Reflecting Structure 20)

[0059] As shown in FIG. 2, the reflecting structure 20 is formed on or
above the transparent electrically-conducting layer 13 in at least part
of the area interposed between the semiconductor structure 11 and the
electrode 3. The reflecting structure is preferably formed in a
predetermined pattern so as to cover substantially the entire of the
semiconductor structure and the transparent electrically-conducting layer
13. In addition, as shown in FIG. 2, the transparent
electrically-insulating film 16 can be interposed as the transparent film
between the transparent electrically-conducting layer 13 and the metal
electrode layer 23. In this case, it is preferable that the
electrically-insulating film 16 is at least partially opened, and the
transparent electrically-conducting layer 13 is exposed in the
partially-opened areas. Also, the electrically-insulating film 16 can be
arranged in the reflecting structure 20 and serve as the reflective layer
16.

[0060] The electrically-insulating film 16 serves to efficiently reflect
light from the light emitting device 10. Therefore, the
electrically-insulating film 16 is preferably formed of an oxide
containing at least one element selected from the group consisting of Si
and Al. Specifically, the electrically-insulating film can be formed of
SiO2, Al2O3, or the like. The electrically-insulating film
can be more preferably formed of SiO2. Also, it is preferable that
the thickness of the electrically-insulating film 16 is not less than 200
nm, for example, about 100 nm to 2 μm. In particular, in the case
where a metal electrode layer is formed in the upper surface of the
electrically-insulating film 16, or in the case where the
electrically-insulating film is formed as the reflecting structure 20, it
is preferable that the thickness of the electrically-insulating film 16
falls within the range of 10 to 500 nm.

[0061] In the example of FIG. 2, the reflecting structure 20 includes the
reflective layer 16 of electrically-insulating film, and the dielectric
multilayer film 4 which is additionally formed on or above the reflective
layer 16. The reflective layer 16 extends under the dielectric multilayer
film 4 as viewed in plan view.

(Dielectric Multilayer Film 4)

[0062] The dielectric multilayer film 4 is formed as a multilayer
structure where two or more types of dielectric layers with different
refractive indices are alternately formed on each other. Specifically,
alternately formed on each other are the different-refractive-index
dielectric layers having thickness of 1/4 of the wavelength of light so
that the light with the predetermined wavelength can be efficiently
reflected. The dielectric multilayer film 4 is preferably formed of a
material of at least one oxide or nitride containing an element selected
from the group consisting of Si, Ti, Zr, Nb, Ta and Al. In particular,
the dielectric multilayer film 4 more preferably includes at least two
oxides/nitrides containing an element selected from the group consisting
of Si, Ti, Zr, Nb, Ta and Al with the at least two oxides/nitrides being
repeatedly arranged on each other. The dielectric multilayer film 4 is
preferably formed as a laminated structure which is formed of nonmetallic
materials or oxides, for example, is formed of
(SiO2/TiO2)n (n is a natural number). Also, in the two
types of dielectric layers with different refractive indices, the
lower-refractive-index dielectric layer can be formed of SiO2, while
the higher-refractive-index dielectric layer can be formed of
Nb2O5, TiO2, ZrO2, Ta2O5, or the like.
According to this construction, as compared with metal materials, the
loss by light absorption of the reflective layer 16 can be reduced.

[0063] Also, the dielectric multilayer film 4 preferably consists of two
to five pairs of, more preferably three to four pairs of,
different-refractive-index dielectric layers with the pairs of
different-refractive-index dielectric layers being arranged on each
other. In addition, it is preferable that the total thickness of the
dielectric multilayer film 4 is 0.2 to 1 μm, more preferably, 0.3 to
0.6 μm. According to this construction, it is possible to suppress
that the dielectric multilayer interferential action causes sharp drop in
light transmittance. Accordingly, it is possible to provide high
reflectivity continuously in wide wavelength range. As a result, even if
the center wavelength of reflecting structure is longer than the light
emission peak wavelength of a light source, it is possible to suppress
reduction of the reflectivity of perpendicularly-incident light. That is,
it is possible to reflect not only light from the light source incident
on the reflecting structure 20 at a certain incidence angle but also
light incident on the reflecting structure at a small incidence angle.
Therefore, it is possible to relatively increase the light output of
light emitting device.

(Reflective Layer 16)

[0064] The reflective layer 16 is formed under the bottom surface of the
dielectric multilayer film 4. The refractive index of the reflective
layer 16 is lower than the refractive index of the semiconductor
structure 11. According to this construction, when light is incident from
the light-emitting layer 8 on the reflective layer 16, the light can be
efficiently reflected toward the light outgoing side. Specifically, it is
preferable that the refractive index falls within the range of 1.45 to
1.68. In this range, it is possible to effectively reflect the light
incident from the semiconductor structure 11 on the reflective layer 16
at a certain angle.

[0065] The reflective layer 16 in the nitride semiconductor device 10
shown in FIG. 2 is formed of SiO2. According to this construction,
more than 80% of emitted light can be reflected which is incident from
the light-emitting layer 8 on the reflective layer 16 at angles not lower
than 37° where the angle of perpendicular-incident light from the
light-emitting layer 8 on the reflective layer 16 is defined 0°.
In addition, the reflective layer 16 can also serve as the
electrically-insulating film 16. The reflective layer is preferable since
the reflective layer can have both electrically insulating function and
light reflective function. In addition, the dielectric multilayer 4 and
additionally the later-discussed metal reflective layer can reflect light
which is incident at angles not greater lower than 37°.
Specifically, the thickness of the dielectric multilayer 4 is adjusted
which is formed on or above the reflective layer 16 in the reflecting
structure 20. The center wavelength of the reflection spectrum is
adjusted to 1.05 to 1.35 times the light emitting peak wavelength of the
light-emitting layer. According to this construction, the light can be
efficiently reflected which passes the reflective layer 16. As a result,
the total reflectivity by the reflecting structure 20 can be
substantially 100%.

[0066] The reflectivity of the reflective layer 16 of SiO2 can be
increased by increasing its thickness. FIG. 5 shows the luminous flux
relative value variation with the thickness of the reflective layer 16 of
SiO2. As illustrated, the luminous flux relative value is gradually
increased until the thickness reaches 5000 Å, and reaches
substantially a saturation value at the 5000 Å. It can be said that
this shows that stable luminous flux can be provided in the case where
the thickness of the reflective film is not less than 5000 Å.

(Electrode)

[0067] After the reflecting structure 20 containing the dielectric
multilayer film 4 is formed on or above the transparent
electrically-conducting layer 13, as shown in FIG. 2, the metal electrode
layer 23 is formed, and is electrically connected to the transparent
electrically-conducting layer 13. The metal electrode layer 23 is in
contact with the transparent electrically-conducting layer 13 and the
dielectric multilayer film 4. Again, the transparent
electrically-conducting layers 13 are suitably arranged on the p-type
semiconductor layer 7 side and on n-type semiconductor layer 6 side. The
dielectric multilayer film 4 composes the reflecting structure 20. The
metal electrode layers 23 are formed on the first electrode 3A side and
the second electrode 3B side.

[0068] The metal electrode layer 23 is arranged at least partially in the
surface of the multilayer film 4, and serves as a metallic reflective
layer having an optical characteristic which efficiently reflects light
traveling toward the metallic reflective layer. It is preferable that the
metal electrode layer 23 is arranged substantially in the entire of the
reflecting structure surface. In addition, the metal electrode layers
also serve as pad electrodes which electrically connect the light
emitting device to exterior terminals. For example,
electrically-conducting members such as Au bumps are formed on the metal
electrode layer surfaces so that the electrodes of the light emitting
device are electrically connected through the electrically-conducting
members to the exterior terminals, which are opposed the electrodes of
the light emitting device. Parts of the metal electrode layer are
directly electrically connected to the transparent
electrically-conducting layer 13. Suitable existing structures can be
used as the pad electrode. For example, the pad electrode can be formed
of any metal or any alloy of Al, Cu, Au, Pt, Pd, Rh, Ni, W, Mo, Cr and
Ti, or combination of them. An example of the metal electrode layer can
be provided by a laminated structure constructed of W/Pt/Au, Rh/Pt/Au,
W/Pt/Au/Ni, Pt/Au, or Ti/Rh. Each of the elements are formed on other
element in this order from the lower surface side in W/Pt/Au, Rh/Pt/Au,
W/Pt/Au/Ni, Pt/Au, or Ti/Rh.

[0069] In the first embodiment 1, the metal electrode layer 23 is formed
in at least partial contact with the reflecting structure 20 and the
transparent electrically-conducting layer 13. In a modified embodiment,
the metal electrode layer 23 may have contact portions as parts of the
metal electrode layer 23 which extend in through holes formed the
transparent electrically-conducting layer 13. Alternatively, the metal
electrode layer 23 may have contact portions which are arranged outside
the transparent electrically-conducting layer 13 and are in direct
contact with the nitride semiconductor layer. In these cases, the contact
portions as parts of the metal electrode layer can increase bonding
strength of the metal electrode layer.

[0070] It is preferable that the metal electrode layers 23 are formed of
the same metals with the same thickness when being formed on the p-type
nitride semiconductor layer 7 side and the n-type nitride semiconductor
layer 6 side. The reason is that both the metal electrode layers can be
simultaneously formed. In this case, it is possible to simplify the
formation process of the metal electrode layers as compared with the case
where the metal electrode layers are formed in separate formation
processes. In the case where the metal electrode layers are formed in
separate formation processes, the electrode on the n-type nitride
semiconductor layer side can be constructed as W/Pt/Au electrode (e.g.,
thicknesses 20/200/500 nm), W/Pt/Au/Ni electrode with Ni additionally
formed on W/Pt/Au electrode, Ti/Rh/Pt/Au electrode, or the like. In the
embodiment shown in FIG. 2, the metal electrode layer 23 is constructed
of Ti/Rh, which has high reflectivity and weatherability.

(Protective Film)

[0071] After the metal electrode layer 23 is formed, the
electrically-insulating protective film can be formed substantially in
the entire surface of the semiconductor light emitting device 10 except
the connection areas to be connected to the external terminals. That is,
openings are formed in the protective film which covers the n-type
electrode 3A portion and the p-type electrode 3B portion. The protective
film can be formed of SiO2, TiO2, Al2O3, polyimide,
or the like.

[0072] The light emitting device according to the aforementioned
embodiment has been described which has the mount surface with the p and
n electrodes, and a back surface as the light-outgoing surface. However,
the light emitting device according to the present invention is not
limited to this. The light emitting device according to the present
invention can has the light-outgoing surface with p and n electrodes, and
the back surface as the mount surface. In this case, the substrate side
is mounted, while the p and n electrodes are wired by wirebonding or the
like. Although these exemplary light emitting devices has the p and n
electrodes are arranged on the same surface, the light emitting device
according to the present invention is not limited to this construction.
The present invention can be applied to a light emitting device having a
pair of electrodes which are arranged above and under the light-emitting
layer with the light-emitting layer being interposed between the pair of
electrodes (i.e., vertical type light emitting device). In the case of
the vertical type light emitting device, the reflective layer 16 is
arranged at least in the electrode on the wiring board side onto which
the light emitting device is mounted. Thus, when light is incident on the
reflective layer 16, the light can be reflected toward the light outgoing
side opposed to the device-mount wiring substrate side. In the case where
the reflecting structure 20 is additionally formed in the electrode which
is formed on the light outgoing surface side, light absorption by the
electrode can be suppressed. As a result, it is possible to external
quantum efficiency.

(Light Emitting Apparatus)

[0073] The thus-constructed light emitting device is mounted onto the
wiring board in a flip-chip mounting manner so that the light emitting
apparatus is provided. An exemplary production method of the light
emitting apparatus 1 shown in FIG. 1 is now described. The bumps are
first formed on a wafer used as the submount substrate 9 in patterns for
mounting the light emitting device 10 in a flip-chip mounting manner.
Subsequently, the light emitting device 10 is mounted by the bumps in a
flip-chip mounting manner. A metal mask is formed on the wafer by screen
printing. Resin for forming the covering layer is applied on the metal
mask, and is spread by a squeegee. After the resin is cured, the metal
mask is removed. The wafer is cut by dicing, and is divided into submount
boards with a submount board size. The cut submount substrate 9 is fixed
onto a support member through an eutectic layer by eutectic die-bonding.
The terminals of the submount board 9 are connected to terminals of the
support member by wire-bonding. A lens formed of resin is fixed by an
adhesive or the like so as to surround the periphery of the LED chip.
Thus, the light emitting apparatus is provided.

[0074] Leads 52 and 53 of the light emitting apparatus 1 are sealed by a
transparent sealing member as shown in FIG. 4. A light emitting device 50
is arranged in a mount portion of one mount lead 52. A lens portion 54 as
a sealing member is arranged in an upper part of the mount portion.

[0075] The material of the sealing member is not specifically limited as
long as it is transparent. Although the sealing member is preferably
formed of a silicone resin composition, a denatured silicone resin
composition or the like, a transparent, electrically-insulating resin
composition may be used such as epoxy resin composition, denatured epoxy
resin composition and acrylic resin composition or the like. In addition,
the sealing member can be formed of a high weather-resistant material
such as hybrid resin containing at least one or more types of the resins.
Also, a high light-resistant inorganic material may be used such as glass
and silica gel. The light-outgoing side of the sealing member can be
formed in a desired shape so that the sealing member has a lens effect.

(Additive Member)

[0076] The sealing member can contain suitable members (e.g., wavelength
conversion member, viscosity adjusting agent, pigment, and phosphor)
depending on the applications. According to this construction, it is
possible to the light emitting apparatus with excellent directivity.
Similarly, various types of coloring agents can be added as a filter
material which provides a filter effect for cutting off external entering
light and light with unnecessary wavelength from the light emitting
device. Also, the sealing member can contain a filler in addition to a
phosphor. Specifically, materials similar to the diffusion materials can
be used as a material of the filler. However, the filler has a center
particle size different from the diffusion agent. The filler preferably
has a center particle size of not less than 5 μm to not more than 100
μm. In the case where the sealing member contains the filler with such
a center particle size, chromaticity unevenness of the light emitting
apparatus can be improved by light dispersion, and additionally thermal
shock resistance of the sealing member can be improved.

[0077] Although the light emitting peak wavelength of emitted light is not
specifically limited which is emitted from the light-emitting layer of
the light emitting device in the light emitting apparatus, the
semiconductor light emitting device can have a light emission spectrum in
the near-ultraviolet range to the short wavelength visible light range
(about 240 to 650 nm), for example. The semiconductor light emitting
device preferably has a light emission spectrum in the range of 360 to
420 nm, or 450 to 650 nm.

(Intermediate Layer 17)

[0078] In the case of a semiconductor light emitting device shown in FIG.
8A, when the transparent electrically-conducting layer 13 is formed of
ITO, and a reflection multilayer extension portion is formed of SiO2
which is the reflective layer 16 of the bottom layer of a reflection
multilayer film, due to chemical reaction of ITO with SiO2, the
electrical resistance of the transparent electrically-conducting layer
increases with the total operating time. For this reason, there is a
problem that the operating voltage Vf (i.e., forward voltage) of the
semiconductor light emitting device will increase. This increase of
forward voltage Vf will shorten the span of time until it is determined
that the device cannot properly operate any more, in other words, that
the life of the device expires. In addition, since the bonding strength
of the contact interface between ITO and SiO2 is weak, the
transparent electrically-conducting layer may peel off the reflection
multilayer film, which in turn will cause device failure. For this
reason, there is a problem that the life of the device may also be short.

[0079] In order to suppress such electric/mechanical deterioration of the
device and to increase the life of device, according to this embodiment,
an intermediate layer 17 is interposed between the transparent
electrically-conducting layer 13 and the reflecting structure 20, as
shown in FIG. 2A. That is, it is conceivable that the transparent
electrically-conducting layer 13 is oxidized by chemical reaction with
the reflecting structure 20 of the electrode. Accordingly, a material
containing an element with larger ionization tendency is arranged in the
upper surface of the transparent electrically-conducting layer 13 so that
such oxidation reaction is suppressed. Thus, the rise of the resistance
(i.e., Vf) can be suppressed. The intermediate layer is interposed
between the transparent electrically-conducting layer and the reflecting
structure, and can serve as a voltage-rise preventing layer which
prevents the rise of the forward voltage.

[0080] The intermediate layer 17 can be formed of Nb2O5,
Al2O3 or TiO2 as a material which contains an element with
larger ionization tendency than the reflective layer 16. Also, the
intermediate layer 17 can be formed of SiN as a material which does not
substantially contain oxygen in the composition of the material, or the
like. In particular, in the case where the intermediate layer 17 is
formed of the same material as any of the layers in the dielectric
multilayer film 4 which composes the reflecting structure 20, any
additional target material is not required when the intermediate layer 17
is deposited. Therefore, it is possible to improve the efficiency of the
manufacture processes and to keep the cost in check. From this viewpoint,
the intermediate layer 17 is preferably formed of Nb2O5.

[0081] The intermediate layer 17 preferably has a thickness in the range
of 270 to 540 Å. If the thickness of the intermediate layer is
smaller than this range, the life characteristic of the device will
decrease. If the thickness of the intermediate layer is greater than this
range, the output of the device will decrease.

(Durability Test)

[0082] A durability test is conducted to confirm whether the rise of Vf is
suppressed when the intermediate layer 17 is additionally formed.
Specifically, a semiconductor light emitting device according to an
example 1 is formed which includes the intermediate layer 17 with 540
Å formed of Nb2O5, while a known semiconductor light
emitting device according to a comparative example 1 is formed which does
not the intermediate layer. The semiconductor light emitting devices
continuously operate for 1000 hours with the temperatures of the
light-emitting layer being held at 152° and 172° C. under a
continuously-operating test. The rise rate of operating voltage is
measured from the start of operation at driving current 350 mA (rated
current). Specifically, in the example 1, the intermediate layer 17 is
formed of Nb2O5. The transparent electrically-conducting layer
13 is formed of ITO and has a thickness 800 Å. The reflecting
structure 20 is formed which includes an SiO2 layer with thickness
5000 Å, and three pairs of Nb2O5/SiO2 as the
dielectric multilayer film 4. The pairs of Nb2O5/SiO2 are
formed on each other. The eutectic electrode is formed of Pt/Au. The
semiconductor light emitting device according to the comparative example
is formed under the same conditions except that the Nb2O5 is
not included. In the comparative example 1, the rises of operating
voltage are 2.6% and 3.7% at temperatures of the light-emitting layer
152° and 172° C., respectively. According to the result,
the rise of operating voltage gets larger with the temperature of the
light-emitting layer. In the example 1, the rises of operating voltage
are 1.3% and 1.5% at temperatures of the light-emitting layer 152°
and 172° C., respectively. The rise of operating voltage almost
does not vary with the temperature of the light-emitting layer. The
suppression of Vf rise can be confirmed.

(Sharing Test)

[0083] In order to confirm the effect of the additionally-formed
intermediate layer 17 on the strength improvement of the contact
interface between the transparent electrically-conducting layer 13 and
the electrode structure, samples of the semiconductor light emitting
devices according to the example 1 and the comparative example 1 are
formed as shown in FIG. 6, and a sharing test is conducted. FIG. 7 is a
graph showing the result. In the comparative example 1, peering occurs
both in the interfaces between the p-type semiconductor layer and the
transparent electrically-conducting layer 13, and the transparent
electrically-conducting layer 13 and the reflective layer 16. In
particular, in the comparative example 1, peeling is found both in the
peeling interface of GaN/ITO, and the peeling interface between ITO and
SiO2. In the example 1, as shown in FIG. 7, peeling occurs only in
the interface between the p-type semiconductor layer and the transparent
electrically-conducting layer 13. According to the result, it can be
conformed that, when the intermediate layer 17 of Nb2O5 is
additionally formed, peeling is prevented in the interface between ITO as
the transparent electrically-conducting layer 13 and Nb2O5, in
other words, the bonding strength in the bonding surface between ITO and
Nb2O5 is stronger than the bonding interface between ITO and
SiO2.

INDUSTRIAL APPLICABILITY

[0084] A light emitting device according to the present invention can be
applied to a lighting light source, an LED display, a back light source,
a signal light, an illuminated switch, various types of sensors and
indicators, and the like.

[0085] It should be apparent to those with an ordinary skill in the art
that while various preferred embodiments of the invention have been shown
and described, it is contemplated that the invention is not limited to
the particular embodiments disclosed, which are deemed to be merely
illustrative of the inventive concepts and should not be interpreted as
limiting the scope of the invention, and which are suitable for all
modifications and changes falling within the scope of the invention as
defined in the appended claims.

[0086] The present application is based on Applications No. 2011-086,821
filed in Japan on Apr. 8, 2011, and No. 2012-25,525 filed in Japan on
Feb. 8, 2012, the contents of which are incorporated herein by
references.